1700. The conclusion I have arrived at is, that it is the molecules of the substance which polarize as wholes (1347.); and that however complicated the composition of a body may be, all those particles or atoms which are held together by chemical affinity to form one molecule of the resulting body act as one conducting mass or particle when inductive phenomena and polarization are produced in the substance of which it is a part.

1701. This conclusion is founded on several considerations. Thus if we observe the insulating and conducting power of elements when they are used as dielectrics, we find some, as sulphur, phosphorus, chlorine, iodine, &c., whose particles insulate, and therefore polarize in a high degree; whereas others, as the metals, give scarcely any indication of possessing a sensible proportion of this power (1328.), their particles freely conducting one to another. Yet when these enter into combination they form substances having no direct relation apparently, in this respect, to their elements; for water, sulphuric acid, and such compounds formed of insulating elements, conduct by comparison freely; whilst oxide of lead, flint glass, borate of lead, and other metallic compounds containing very high proportions of conducting matter, insulate excellently well. Taking oxide of lead therefore as the illustration, I conceive that it is not the particles of oxygen and lead which polarize separately under the act of induction, but the molecules of oxide of lead which exhibit this effect, all the elements of one particle of the resulting body, being held together as parts of one conducting individual by the bonds of chemical affinity; which is but another term for electrical force (918.).

1702. In bodies which are electrolytes we have still further reason for believing in such a state of things. Thus when water, chloride of tin, iodide of lead, &c. in the solid state are between the electrodes of the voltaic battery, their particles polarize as those of any other insulating dielectric do (1164.); but when the liquid state is conferred on these substances, the polarized particles divide, the two halves, each in a highly charged state, travelling onwards until they meet other particles in an opposite and equally charged state, with which they combine, to the neutralization of their chemical, i.e. their electrical forces, and the reproduction of compound particles, which can again polarize as wholes, and again divide to repeat the same series of actions (1347.).

1703. But though electrolytic particles polarize as wholes, it would appear very evident that in them it is not a matter of entire indifference how the particle polarizes (1689.), since, when free to move (380, &c.) the polarities are ultimately distributed in reference to the elements; and sums of force equivalent to the polarities, and very definite in kind and amount, separate, as it were, from each other, and travel onwards with the elementary particles. And though I do not pretend to know what an atom is, or how it is associated or endowed with electrical force, or how this force is arranged in the cases of combination and decomposition, yet the strong belief I have in the electrical polarity of particles when under inductive action, and the hearing of such an opinion on the general effects of induction, whether ordinary or electrolytic, will be my excuse, I trust, for a few hypothetical considerations.

1704 In electrolyzation it appears that the polarized particles would (because of the gradual change which has been induced upon the chemical, i.e. the electrical forces of their elements (918.)) rather divide than discharge to each other without division (1348.); for if their division, i.e. their decomposition and recombination, be prevented by giving them the solid state, then they will insulate electricity perhaps a hundredfold more intense than that necessary for their electrolyzation (419, &c.). Hence the tension necessary for direct conduction in such bodies appears to be much higher than that for decomposition (419. 1164. 1344.).

1705. The remarkable stoppage of electrolytic conduction by solidification (380. 1358.), is quite consistent with these views of the dependence of that process on the polarity which is common to all insulating matter when under induction, though attended by such peculiar electro-chemical results in the case of electrolytes. Thus it may be expected that the first effect of induction is so to polarize and arrange the particles of water that the positive or hydrogen pole of each shall be from the positive electrode and towards the negative electrode, whilst the negative or oxygen pole of each shall be in the contrary direction; and thus when the oxygen and hydrogen of a particle of water have separated, passing to and combining with other hydrogen and oxygen particles, unless these new particles of water could turn round they could not take up that position necessary for their successful electrolytic polarization. Now solidification, by fixing the water particles and preventing them from assuming that essential preliminary position, prevents also their electrolysis (413.); and so the transfer of forces in that manner being prevented (1347. 1703.), the substance acts as an ordinary insulating dielectric (for it is evident by former experiments (419. 1704.) that the insulating tension is higher than the electrolytic tension), induction through it rises to a higher degree, and the polar condition of the molecules as wholes, though greatly exalted, is still securely maintained.

1706. When decomposition happens in a fluid electrolyte, I do not suppose that all the molecules in the same sectional plane (1634.) part with and transfer their electrified particles or elements at once. Probably the discharge force for that plane is summed up on one or a few particles, which decomposing, travelling and recombining, restore the balance of forces, much as in the case of spark disruptive discharge (1406.); for as those molecules resulting from particles which have just transferred power must by their position (1705.) be less favourably circumstanced than others, so there must be some which are most favourably disposed, and these, by giving way first, will for the time lower the tension and produce discharge.

1707. In former investigations of the action of electricity (821, &c.) it was shown, from many satisfactory cases, that the quantity of electric power transferred onwards was in proportion to and was definite for a given quantity of matter moving as anion or cathion onwards in the electrolytic line of action; and there was strong reason to believe that each of the particles of matter then dealt with, had associated with it a definite amount of electrical force, constituting its force of chemical affinity, the chemical equivalents and the electro-chemical equivalents being the same (836.). It was also found with few, and I may now perhaps say with no exceptions (1341.), that only those compounds containing elements in single proportions could exhibit the characters and phenomena of electrolytes (697.); oxides, chlorides, and other bodies containing more than one proportion of the electro-negative element refusing to decompose under the influence of the electric current.

1708. Probable reasons for these conditions and limitations arise out of the molecular theory of induction. Thus when a liquid dielectric, as chloride of tin, consists of molecules, each composed of a single particle of each of the elements, then as these can convey equivalent opposite forces by their separation in opposite directions, both decomposition and transfer can result. But when the molecules, as in the bichloride of tin, consist of one particle or atom of one element, and two of the other, then the simplicity with which the particles may be supposed to be arranged and to act, is destroyed. And, though it may be conceived that when the molecules of bichloride of tin are polarized as wholes by the induction across them, the positive polar force might accumulate on the one particle of tin whilst the negative polar force accumulated on the two particles of chlorine associated with it, and that these might respectively travel right and left to unite with other two of chlorine and one of tin, in analogy with what happens in cases of compounds consisting of single proportions, yet this is not altogether so evident or probable. For when a particle of tin combines with two of chlorine, it is difficult to conceive that there should not be some relation of the three in the resulting molecule analogous to fixed position, the one particle of metal being perhaps symmetrically placed in relation to the two of chlorine: and, it is not difficult to conceive of such particles that they could not assume that position dependent both on their polarity and the relation of their elements, which appears to be the first step in the process of electrolyzation (1345. 1705.).

S 21. Relation of the electric and magnetic forces.

1709. I have already ventured a few speculations respecting the probable relation of magnetism, as the transverse force of the current, to the divergent or transverse force of the lines of inductive action belonging to static electricity (1658, &c.).

1710. In the further consideration of this subject it appeared to me to be of the utmost importance to ascertain, if possible, whether this lateral action which we call magnetism, or sometimes the induction of electrical currents (26. 1048, &c.), is extended to a distance by the action of the intermediate particles in analogy with the induction of static electricity, or the various effects, such as conduction, discharge, &c., which are dependent on that induction; or, whether its influence at a distance is altogether independent of such intermediate particles (1662.).

1711. I arranged two magneto-electric helices with iron cores end to end, but with an interval of an inch and three quarters between them, in which interval was placed the end or pole of a bar magnet. It is evident, that on moving the magnetic pole from one core towards the other, a current would tend to form in both helices, in the one because of the lowering, and in the other because of the strengthening of the magnetism induced in the respective soft iron cores. The helices were connected together, and also with a galvanometer, so that these two currents should coincide in direction, and tend by their joint force to deflect the needle of the instrument. The whole arrangement was so effective and delicate, that moving the magnetic pole about the eighth of an inch to and fro two or three times, in periods equal to those required for the vibrations of the galvanometer needle, was sufficient to cause considerable vibration in the latter; thus showing readily the consequence of strengthening the influence of the magnet on the one core and helix, and diminishing it on the other.

1712. Then without disturbing the distances of the magnet and cores, plates of substances were interposed. Thus calling the two cores A and B, a plate of shell-lac was introduced between the magnetic pole and A for the time occupied by the needle in swinging one way; then it was withdrawn for the time occupied in the return swing; introduced again for another equal portion of time; withdrawn for another portion, and so on eight or nine times; but not the least effect was observed on the needle. In other cases the plate was alternated, i.e. it was introduced between the magnet and A for one period of time, withdrawn and introduced between the magnet and B for the second period, withdrawn and restored to its first place for the third period, and so on, but with no effect on the needle.

1713. In these experiments shell-lac in plates 0.9 of an inch in thickness, sulphur in a plate 0.9 of an inch in thickness, and copper in a plate 0.7 of an inch in thickness were used without any effect. And I conclude that bodies, contrasted by the extremes of conducting and insulating power, and opposed to each other as strongly as metals, air, and sulphur, show no difference with respect to magnetic forces when placed in their lines of action, at least under the circumstances described.

1714. With a plate of iron, or even a small piece of that metal, as the head of a nail, a very different effect was produced, for then the galvanometer immediately showed its sensibility, and the perfection of the general arrangement.

1715. I arranged matters so that a plate of copper 0.2 of an inch in thickness, and ten inches in diameter, should have the part near the edge interposed between the magnet and the core, in which situation it was first rotated rapidly, and then held quiescent alternately, for periods according with that required for the swinging of the needle; but not the least effect upon the galvanometer was produced.

1716. A plate of shell-lac 0.6 of an inch in thickness was applied in the same manner, but whether rotating or not it produced no effect.

1717. Occasionally the plane of rotation was directly across the magnetic curve: at other times it was made as oblique as possible; the direction of the rotation being also changed in different experiments, but not the least effect was produced.

1718. I now removed the helices with their soft iron cores, and replaced them by two flat helices wound upon card board, each containing forty-two feet of silked copper wire, and having no associated iron. Otherwise the arrangement was as before, and exceedingly sensible; for a very slight motion of the magnet between the helices produced an abundant vibration of the galvanometer needle.

1719. The introduction of plates of shell-lac, sulphur, or copper into the intervals between the magnet and these helices (1713.), produced not the least effect, whether the former were quiescent or in rapid revolution (1715.). So here no evidence of the influence of the intermediate particles could be obtained (1710.).

1720. The magnet was then removed and replaced by a flat helix, corresponding to the two former, the three being parallel to each other. The middle helix was so arranged that a voltaic current could be sent through it at pleasure. The former galvanometer was removed, and one with a double coil employed, one of the lateral helices being connected with one coil, and the other helix with the other coil, in such manner that when a voltaic current was sent through the middle helix its inductive action (26.) on the lateral helices should cause currents in them, having contrary directions in the coils of the galvanometer. By a little adjustment of the distances these induced currents were rendered exactly equal, and the galvanometer needle remained stationary notwithstanding their frequent production in the instrument. I will call the middle coil C, and the external coils A and B.

1721. A plate of copper 0.7 of an inch thick and six inches square, was placed between coils C and B, their respective distances remaining unchanged; and then a voltaic current from twenty pairs of 4 inch plates was sent through the coil C, and intermitted, in periods fitted to produce an effect on the galvanometer (1712.). if any difference had been produced in the effect of C on A and B. But notwithstanding the presence of air in one interval and copper in the other, the inductive effect was exactly alike on the two coils, and as if air had occupied both intervals. So that notwithstanding the facility with which any induced currents might form in the thick copper plate, the coil outside of it was just as much affected by the central helix C as if no such conductor as the copper had been there (65.).

1722. Then, for the copper plate was substituted one of sulphur 0.9 of an inch thick; still the results were exactly the same, i.e. there was no action at the galvanometer.

1723. Thus it appears that when a voltaic current in one wire is exerting its inductive action to produce a contrary or a similar current in a neighbouring wire, according as the primary current is commencing or ceasing, it makes not the least difference whether the intervening space is occupied by such insulating bodies as air, sulphur and shell-lac, or such conducting bodies as copper, and the other non-magnetic metals.

1724. A correspondent effect was obtained with the like forces when resident in a magnet thus. A single flat helix (1718.) was connected with a galvanometer, and a magnetic pole placed near to it; then by moving the magnet to and from the helix, or the helix to and from the magnet, currents were produced indicated by the galvanometer.

1725. The thick copper plate (1721.) was afterwards interposed between the magnetic pole and the helix; nevertheless on moving these to and fro, effects, exactly the same in direction and amount, were obtained as if the copper had not been there. So also on introducing a plate of sulphur into the interval, not the least influence on the currents produced by motion of the magnet or coils could be obtained.

1726. These results, with many others which I have not thought it needful to describe, would lead to the conclusion that (judging by the amount of effect produced at a distance by forces transverse to the electric current, i.e. magnetic forces,) the intervening matter, and therefore the intervening particles, have nothing to do with the phenomena; or in other words, that though the inductive force of static electricity is transmitted to a distance by the action of the intermediate particles (1164. 1666.), the transverse inductive force of currents, which can also act at a distance, is not transmitted by the intermediate particles in a similar way.

1727. It is however very evident that such a conclusion cannot be considered as proved. Thus when the metal copper is between the pole and the helix (1715. 1719. 1725.) or between the two helices (1721.) we know that its particles are affected, and can by proper arrangements make their peculiar state for the time very evident by the production of either electrical or magnetical effects. It seems impossible to consider this effect on the particles of the intervening matter as independent of that produced by the inductric coil or magnet C, on the inducteous coil or core A (1715. 1721.); for since the inducteous body is equally affected by the inductric body whether these intervening and affected particles of copper are present or not (1723. 1725.), such a supposition would imply that the particles so affected had no reaction back on the original inductric forces. The more reasonable conclusion, as it appears to me, is, to consider these affected particles as efficient in continuing the action onwards from the inductric to the inducteous body, and by this very communication producing the effect of no loss of induced power at the latter.

1728. But then it may be asked what is the relation of the particles of insulating bodies, such as air, sulphur, or lac, when they intervene in the line of magnetic action? The answer to this is at present merely conjectural. I have long thought there must be a particular condition of such bodies corresponding to the state which causes currents in metals and other conductors (26. 53. 191. 201. 213.); and considering that the bodies are insulators one would expect that state to be one of tension. I have by rotating non-conducting bodies near magnetic poles and poles near them, and also by causing powerful electric currents to be suddenly formed and to cease around and about insulators in various directions, endeavoured to make some such state sensible, but have not succeeded. Nevertheless, as any such state must be of exceedingly low intensity, because of the feeble intensity of the currents which are used to induce it, it may well be that the state may exist, and may be discoverable by some more expert experimentalist, though I have not been able to make it sensible.

1729. It appears to me possible, therefore, and even probable, that magnetic action may be communicated to a distance by the action of the intervening particles, in a manner having a relation to the way in which the inductive forces of static electricity are transferred to a distance (1677.); the intervening particles assuming for the time more or less of a peculiar condition, which (though with a very imperfect idea) I have several times expressed by the term electro-tonic state (60. 242. 1114. 1661.). I hope it will not be understood that I hold the settled opinion that such is the case. I would rather in fact have proved the contrary, namely, that magnetic forces are quite independent of the matter intervening between the inductric and the inductions bodies; but I cannot get over the difficulty presented by such substances as copper, silver, lead, gold, carbon, and even aqueous solutions (201. 213.), which though they are known to assume a peculiar state whilst intervening between the bodies acting and acted upon (1727.), no more interfere with the final result than those which have as yet had no peculiarity of condition discovered in them.

1730. A remark important to the whole of this investigation ought to be made here. Although I think the galvanometer used as I have described it (1711. 1720.) is quite sufficient to prove that the final amount of action on each of the two coils or the two cores A and B (1713. 1719.) is equal, yet there is an effect which may be consequent on the difference of action of two interposed bodies which it would not show. As time enters as an element into these actions[A] (125.), it is very possible that the induced actions on the helices or cores A, B, though they rise to the same degree when air and copper, or air and lac are contrasted as intervening substances, do not do so in the same time; and yet, because of the length of time occupied by a vibration of the needle, this difference may not be visible, both effects rising to their maximum in periods so short as to make no sensible portion of that required for a vibration of the needle, and so exert no visible influence upon it.

[A] See Annnles de Chimie, 1833, tom. li. pp. 422, 428.

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1731. If the lateral or transverse force of electrical currents, or what appears to be the same thing, magnetic power, could be proved to be influential at a distance independently of the intervening contiguous particles, then, as it appears to me, a real distinction of a high and important kind, would be established between the natures of these two forces (1654. 1664.). I do not mean that the powers are independent of each other and might be rendered separately active, on the contrary they are probably essentially associated (1654.), but it by no means follows that they are of the same nature. In common statical induction, in conduction, and in electrolyzation, the forces at the opposite extremities of the particles which coincide with the lines of action and have commonly been distinguished by the term electric, are polar, and in the cases of contiguous particles act only to insensible distances; whilst those which are transverse to the direction of these lines, and are called magnetic, are circumferential, act at a distance, and if not through the mediation of the intervening particles, have their relations to ordinary matter entirely unlike those of the electrical forces with which they are associated.

1732. To decide this question of the identity or distinction of the two kinds of power, and establish their true relation, would be exceedingly important. The question seems fully within the reach of experiment, and offers a high reward to him who will attempt its settlement.

1733. I have already expressed a hope of finding an effect or condition which shall be to statical electricity what magnetic force is to current electricity (1658.). If I could have proved to my own satisfaction that magnetic forces extended their influence to a distance by the conjoined action of the intervening particles in a manner analogous to that of electrical forces, then I should have thought that the natural tension of the lines of inductive action (1659.), or that state so often hinted at as the electro-tonic state (1661. 1662.), was this related condition of statical electricity.

1734. It may be said that the state of no lateral action is to static or inductive force the equivalent of magnetism to current force; but that can only be upon the view that electric and magnetic action are in their nature essentially different (1664.). If they are the same power, the whole difference in the results being the consequence of the difference of direction, then the normal or undeveloped state of electric force will correspond with the state of no lateral action of the magnetic state of the force; the electric current will correspond with the lateral effects commonly called magnetism; but the state of static induction which is between the normal condition and the current will still require a corresponding lateral condition in the magnetic series, presenting its own peculiar phenomena; for it can hardly be supposed that the normal electric, and the inductive or polarized electric, condition, can both have the same lateral relation. If magnetism be a separate and a higher relation of the powers developed, then perhaps the argument which presses for this third condition of that force would not be so strong.

1735. I cannot conclude these general remarks upon the relation of the electric and magnetic forces without expressing my surprise at the results obtained with the copper plate (1724. 1725.). The experiments with the flat helices represent one of the simplest cases of the induction of electrical currents (1720.); the effect, as is well known, consisting in the production of a momentary current in a wire at the instant when a current in the contrary direction begins to pass through a neighbouring parallel wire, and the production of an equally brief current in the reverse direction when the determining current is stopped (26.). Such being the case, it seems very extraordinary that this induced current which takes place in the helix A when there is only air between A and C (1720.). should be equally strong when that air is replaced by an enormous mass of that excellently conducting metal copper (1721.). It might have been supposed that this mass would have allowed of the formation and discharge of almost any quantity of currents in it, which the helix C was competent to induce, and so in some degree have diminished if not altogether prevented the effect in A: instead of which, though we can hardly doubt that an infinity of currents are formed at the moment in the copper plate, still not the smallest diminution or alteration of the effect in A appears (65.). Almost the only way of reconciling this effect with generally received notions is, as it appears to me, to admit that magnetic action is communicated by the action of the intervening particles (1729. 1733.).

1736. This condition of things, which is very remarkable, accords perfectly with the effects observed in solid helices where wires are coiled over wires to the amount of five or six or more layers in succession, no diminution of effect on the outer ones being occasioned by those within.

S 22. Note on electrical excitation.

1737. That the different modes in which electrical excitement takes place will some day or other be reduced under one common law can hardly be doubted, though for the present we are bound to admit distinctions. It will be a great point gained when these distinctions are, not removed, but understood.

1738. The strict relation of the electrical and chemical powers renders the chemical mode of excitement the most instructive of all, and the case of two isolated combining particles is probably the simplest that we possess. Here however the action is local, and we still want such a test of electricity as shall apply to it, to cases of current electricity, and also to those of static induction. Whenever by virtue of the previously combined condition of some of the acting particles (923.) we are enabled, as in the voltaic pile, to expand or convert the local action into a current, then chemical action can be traced through its variations to the production of all the phenomena of tension and the static state, these being in every respect the same as if the electric forces producing them had been developed by friction.

1739. It was Berzelius, I believe, who first spoke of the aptness of certain particles to assume opposite states when in presence of each other (959.). Hypothetically we may suppose these states to increase in intensity by increased approximation, or by heat, &c. until at a certain point combination occurs, accompanied by such an arrangement of the forces of the two particles between themselves as is equivalent to a discharge, producing at the same time a particle which is throughout a conductor (1700.).

1740. This aptness to assume an excited electrical state (which is probably polar in those forming non-conducting matter) appears to be a primary fact, and to partake of the nature of induction (1162.), for the particles do not seem capable of retaining their particular state independently of each other (1177.) or of matter in the opposite state. What appears to be definite about the particles of matter is their assumption of a particular state, as the positive or negative, in relation to each other, and not of either one or other indifferently; and also the acquirement of force up to a certain amount.

1741. It is easily conceivable that the same force which causes local action between two free particles shall produce current force if one of the particles is previously in combination, forming part of an electrolyte (923. 1738.). Thus a particle of zinc, and one of oxygen, when in presence of each other, exert their inductive forces (1740.), and these at last rise up to the point of combination. If the oxygen be previously in union with hydrogen, it is held so combined by an analogous exertion and arrangement of the forces; and as the forces of the oxygen and hydrogen are for the time of combination mutually engaged and related, so when the superior relation of the forces between the oxygen and zinc come into play, the induction of the former or oxygen towards the metal cannot be brought on and increased without a corresponding deficiency in its induction towards the hydrogen with which it is in combination (for the amount of force in a particle is considered as definite), and the latter therefore has its force turned towards the oxygen of the next particle of water; thus the effect may be considered as extended to sensible distances, and thrown into the condition of static induction, which being discharged and then removed by the action of other particles produces currents.

1742. In the common voltaic battery, the current is occasioned by the tendency of the zinc to take the oxygen of the water from the hydrogen, the effective action being at the place where the oxygen leaves the previously existing electrolyte. But Schoenbein has arranged a battery in which the effective action is at the other extremity of this essential part of the arrangement, namely, where oxygen goes to the electrolyte[A]. The first may be considered as a case where the current is put into motion by the abstraction of oxygen from hydrogen, the latter by that of hydrogen from oxygen. The direction of the electric current is in both cases the same, when referred to the direction in which the elementary particles of the electrolyte are moving (923. 962.), and both are equally in accordance with the hypothetical view of the inductive action of the particles just described (1740.).

[A] Philosophical Magazine, 1838, xii. 225, 315. also De la Rive's results with peroxide of manganese. Annales de Chimie, 1836, lxi. p. 40.—Dec. 1838.

1743. In such a view of voltaic excitement, the action of the particles may be divided into two parts, that which occurs whilst the force in a particle of oxygen is rising towards a particle of zinc acting on it, and falling towards the particle of hydrogen with which it is associated (this being the progressive period of the inductive action), and that which occurs when the change of association takes place, and the particle of oxygen leaves the hydrogen and combines with the zinc. The former appears to be that which produces the current, or if there be no current, produces the state of tension at the termination of the battery; whilst the latter, by terminating for the time the influence of the particles which have been active, allows of others coming into play, and so the effect of current is continued.

1744. It seems highly probable, that excitement by friction may very frequently be of the same character. Wollaston endeavoured to refer such excitement to chemical action[A]; but if by chemical action ultimate union of the acting particles is intended, then there are plenty of cases which are opposed to such a view. Davy mentions some such, and for my own part I feel no difficulty in admitting other means of electrical excitement than chemical action, especially if by chemical action is meant a final combination of the particles.

[A] Philosophical Transactions, 1801, p. 427.

1745. Davy refers experimentally to the opposite states which two particles having opposite chemical relations can assume when they are brought into the close vicinity of each other, but not allowed to combine[A]. This, I think, is the first part of the action already described (1743.); but in my opinion it cannot give rise to a continuous current unless combination take place, so as to allow other particles to act successively in the same manner, and not even then unless one set of the particles be present as an element of an electrolyte (923. 963.); i.e. mere quiescent contact alone without chemical action does not in such cases produce a current.

[A] Philosophical Transactions, 1807, p. 31.

1746. Still it seems very possible that such a relation may produce a high charge, and thus give rise to excitement by friction. When two bodies are rubbed together to produce electricity in the usual way, one at least must be an insulator. During the act of rubbing, the particles of opposite kinds must be brought more or less closely together, the few which are most favourably circumstanced being in such close contact as to be short only of that which is consequent upon chemical combination. At such moments they may acquire by their mutual induction (1740.) and partial discharge to each other, very exalted opposite states, and when, the moment after, they are by the progress of the rub removed from each other's vicinity, they will retain this state if both bodies be insulators, and exhibit them upon their complete separation.

1747. All the circumstances attending friction seem to me to favour such a view. The irregularities of form and pressure will cause that the particles of the two rubbing surfaces will be at very variable distances, only a few at once being in that very close relation which is probably necessary for the development of the forces; further, those which are nearest at one time will be further removed at another, and others will become the nearest, and so by continuing the friction many will in succession be excited. Finally, the lateral direction of the separation in rubbing seems to me the best fitted to bring many pairs of particles, first of all into that close vicinity necessary for their assuming the opposite states by relation to each other, and then to remove them from each other's influence whilst they retain that state.

1748. It would be easy, on the same view, to explain hypothetically, how, if one of the rubbing bodies be a conductor, as the amalgam of an electrical machine, the state of the other when it comes from under the friction is (as a mass) exalted; but it would be folly to go far into such speculation before that already advanced has been confirmed or corrected by fit experimental evidence. I do not wish it to be supposed that I think all excitement by friction is of this kind; on the contrary, certain experiments lead me to believe, that in many cases, and perhaps in all, effects of a thermo-electric nature conduce to the ultimate effect; and there are very probably other causes of electric disturbance influential at the same time, which we have not as yet distinguished.

Royal Institution. June, 1838.



INDEX.

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N.B. A dash rule represents the italics immediately preceding it. The references are sometimes to the individual paragraph, and sometimes to that in conjunction with those which follow.

* * * * *

Absolute charge of matter, 1169. —— quantity of electricity in matter, 852, 861, 873. Acetate of potassa, its electrolysis, 749. Acetates, their electrolysis, 774. Acetic acid, its electrolysis, 773. Acid, nitric, formed in air by a spark, 324. ——, or alkali, alike in exciting the pile, 932. ——, transference of, 525. —— for battery, its nature and strength, 1128, 1137. —— ——, nitric, the best, 1138. —— ——, effect of different strengths, 1139. —— in voltaic pile, does not evolve the electricity, 925, 933. —— ——, its use, 925. Acids and bases, their relation in the voltaic pile, 927, 933. Active battery, general remarks on, 1034, 1136. Adhesion of fluids to metals, 1038. Advantages of a new voltaic battery, 1132. Affinities, chemical, opposed voltaically, 891, 904, 910. ——, their relation in the active pile, 949. Air, its attraction by surfaces, 622. ——, charge of, 1173. ——, ——, by brush, 1434, 1441. ——, ——, by glow, 1537, 1543. ——, convective currents in, 1572, 1576, 1581. ——, dark discharge in, 1548. ——, disruptive discharge in, 1359, 1406, 1425, 1526. ——, induction in, 1208, 1215, 1284, 1362. ——, its insulating and conducting power, 411, 1332, 1336, 1362. ——, its rarefaction facilitates discharge, 1375. ——, electrified, 1443. ——, electro-chemical decompositions in, 454, 1623. ——, hot, discharges voltaic battery, 271, 274. ——, poles of, 455, 461, 559. ——, positive and negative brush in, 1467, 1472, 1476. ——, —— glow in, 1526, 1530. ——, —— spark in, 1485. ——, rarefied, brush in, 1451, 1456. ——, retention of electricity on conductors by, 1377, 1398. ——, specific inductive capacity of, 1284. ——, ——, not varied by temperature or pressure, 1287, 1288. Alkali has strong exciting power in voltaic pile, 884, 931, 941. ——, transference of, 525. Amalgamated zinc, its condition, 1000. ——, how prepared, 863. ——, its valuable use, 863, 999. —— battery, 1001. Ammonia, nature of its electrolysis, 748. ——, solution of, a bad conductor, 554, 748. Ampere's inductive results, 78, 255, 379 note. Anions defined, 665, 824. ——, table of, 847. —— related through the entire circuit, 963. ——, their action in the voltaic pile, 924. ——, their direction of transfer, 962, Anode defined, 663. Antimony, its relation to magneto-electric induction, 139. ——, chloride of, not an electrolyte, 690, 796. ——, oxide of, how affected by the electric current, 801. —— supposed new protoxide, 693. —— ——, sulphuret, 694. Animal electricity, its general characters considered, 351. —— is identical with other electricities, 354, 360. ——, its chemical force, 355. ——, enormous amount, 359. ——, evolution of heat, 353, ——, magnetic force, 351. ——, physiological effects, 357. ——, spark, 358. ——, tension, 352. Apparatus, inductive, 1187. See Inductive apparatus. Arago's magnetic phenomena, their nature, 81, 120. ——, reason why no effect if no motion, 126, ——, direction of motion accounted for, 121. ——, due to induced electric currents, 119, 248. ——, like electro-magnetic rotations in principle, 121. ——, not due to direct induction of magnetism, 128, 138, 215, 243, 248. ——, obtained with electro-magnets, 129. ——, produced by conductors only, 130, 215. ——, time an element in, 124. ——, Babbage and Hershel's results explained, 127. Arago's experiment, Sturgeon's form of, 219. Associated voltaic circles, 989. Atmospheric balls of fire, 1611. ——, electricity, its chemical action, 336. Atomic number judged of from electrochemical equivalent, 851. Atoms of matter, 869, 1703. ——, their electric power, 856, 860. Attraction of particles, its influence in Doebereiner's phenomena, 619. Attractions, electric, their force, 1022 note. ——, chemic, produce current force, 852, 918, 947, 996, 1741. ——, —— local force, 852, 921, 947, 959, 1739. ——, hygrometric, 621. Aurora borealis referred to magneto-electric induction, 192. Axis of power, the electric current on, 517, 1627, 1642.

Balls of fire, atmospheric, 1611. Barlow's revolving globe, magnetic effects explained, 137, 160. Barry, decomposed bodies by atmospheric electricity, 338. Bases and acids, their relation in the pile, 927. Battery, Leyden, that generally used, 291. Battery, voltaic, its nature, 856, 989. ——, origin of its power, 878, 989. ——, —— not in contact, 887, 915, ——, —— chemical, 879, 916, 919, 1741. ——, ——, oxidation of the zinc, 919, 944. ——, its circulating force, 858, 1120. ——, its local force, 1120. ——, quantity of electricity circulating, 990. ——, intensity of electricity circulating, 990, 993. ——, intensity of its current, 909, 994. ——, —— increased, 905, 989. ——, its diminution in power, 1035. ——, —— from adhesion of fluid, 1003, 1136. ——, —— —— peculiar state of metal, 1040. ——, —— —— exhaustion of charge, 1042. ——, —— —— irregularity of plates, 1045, 1146. ——, use of metallic contact in, 893, 896. ——, electrolytes essential to it, 921. ——, ——, why, 858, 923. ——, state of metal and electrolyte before contact, 916. ——, conspiring action of associated affinities, 989. ——, purity of its zinc, 1144. ——, use of amalgamated zinc in, 999. ——, plates, their number, 1151. ——, —— size, 1154. ——, —— vicinity, 1148. ——, —— immersion, 1150. ——, —— relative age, 1146. ——, —— foulness, 1145. ——, excited by acid, 880, 926, 1137. ——, —— alkali, 931, 934, 941. ——, —— sulphuretted solutions, 943. ——, the acid, its use, 925, ——, acid for, 1128, 1137. ——, nitric acid best for, 1137. ——, construction of, 989, 1001, 1121. ——, with numerous alternations, 989. ——, Hare's, 1123. ——, general remarks on, 1031. 1136. ——, simultaneous decompositions with, 1156. ——, practical results with, 1136. ——, improved, 1001, 1006, 1120. ——, ——, its construction, 1124. ——, ——, power, 1125, 1128. ——, ——, advantages, 1132. ——, ——, disadvantages, 1132. Batteries, voltaic, compared, 1126. Becquerel, his important secondary results, 745, 784. Berzelius, his view of combustion, 870, 959. Biot's theory of electro-chemical decomposition, 486. Bismuth, its relation to magneto-electric induction, 139. Bodies classed in relation to the electric current, 823. —— classed in relation to magnetism, 255. Bodies electrolyzable, 824. Bonijol decomposed substances by atmospheric electricity, 336. Boracic acid a bad conductor, 408. Brush, electric, 1425. ——, produced, 1425. ——, not affected by nature of conductors, 1454, 1473. ——, is affected by the dielectrics, 1455, 1463, 1475. ——, not dependent on current of air, 1440. ——, proves molecular action of dielectric, 1449, 1450. ——, its analysis, 1427, 1433. ——, nature, 1434, 1441, 1447. ——, form, 1428, 1449, 1451. ——, ramifications, 1439. —— ——, their coalescence, 1453. ——, sound, 1426, 1431. ——, requisite intensity for, 1446. —— has sensible duration, 1437. —— is intermitting, 1427, 1431, 1451. ——, light of, 1444, 1445, 1451. ——, ——, in different gases, 1446, 1454. ——, dark? 1444, 1552. ——, passes into spark, 1448. ——, spark and glow relation of, 1533, 1539, 1542. ——, in gases, 1454, 1463, 1476. ——, oxygen, 1457, 1476. ——, nitrogen, 1458, 1476. ——, hydrogen, 1459, 1476. ——, coal-gas, 1460, 1476. ——, carbonic acid gas, 1461, 1476. ——, muriatic acid gas, 1462, 1476. ——, rare air, 1451, 1455, 1474. ——, oil of turpentine, 1452. ——, positive, 1455, 1467, 1484. ——, negative, 1468, 1472, 1484. ——, ——, of rapid recurrence, 1468, 1491. ——, positive and negative in different gases, 1455, 1475, 1506.

Capacity, specific inductive, 1252. ——. See Specific inductive capacity. Carbonic acid gas facilitates formation of spark, 1463. ——, brush in, 1461, 1476. ——, glow in, 1534. ——, spark in, 1422, 1463. ——, positive and negative brush in, 1476. ——, —— discharge in, 1546. ——, non-interference of, 645, 652. Carbonic oxide gas, interference of, 645, 652. Carrying discharge, 1562. ——. See Discharge convective. Cathode described, 663, 824. Cations, or cathions, described, 665, 824. ——, table of, 817. ——, direction of their transfer, 962. Cations, are in relation through the entire circuit, 963. Characters of electricity, table of, 360. —— the electric current, constant, 1618, 1627. —— voltaic electricity, 268. —— ordinary electricity, 284. —— magneto-electricity, 343. —— thermo-electricity, 349. —— animal electricity, 351. Charge, free, 1684. —— is always induction, 1171, 1177, 1300, 1682. —— on surface of conductors: why, 1301. ——. influence of form on, 1302. ——, —— distance on, 1303. ——, loss of, by convection, 1569. ——, removed from good insulators, 1203. —— of matter, absolute, 1169. —— of air, 1173. —— —— by brush, 1434, 1441. —— —— by glow, 1526, 1537, 1543. —— of particles in air, 1564. —— of oil of turpentine, 1172. —— of inductive apparatus divided, 1208. ——, residual, of a Leyden jar, 1249. ——, chemical, for battery, good, 1137. ——-, ——, weak and exhausted, 1042, 1143. Chemical action, the, exciting the pile is oxidation, 921. —— superinduced by metals, 564. —— —— platina, 564, 617, 630. —— tested by iodide of potassium, 315. Chemical actions, distant, opposed to each other, 891, 910, 1007. Chemical affinity influenced by mechanical forces, 656. —— transferable through metals, 918. —— statical or local, 852, 921, 917, 959. —— current, 852, 918, 947, 996. Chemical decomposition by voltaic electricity, 278, 450, 661. —— common electricity, 309, 453. —— magneto-electricity, 346. —— thermo-electricity, 349. —— animal electricity, 355. ——. See Decomposition electro-chemical. Chemical and electrical forces identical, 877, 918, 947, 960, 965, 1031. Chloride of antimony not an electrolyte, 690. —— lead, its electrolysis, 794, 815. —— ——, electrolytic intensity for, 978. —— silver, its electrolysis, 541, 813, 902. —— ——, electrolytic intensity for, 979. —— tin, its electrolysis, 789, 819. Chlorides in solution, their electrolysis, 766. —— fusion, their electrolysis, 789, 813. Circle of anions and cathions, 963. Circles, simple voltaic, 875. ——, associated voltaic, 989. Circuit, voltaic, relation of bodies in, 962. Classification of bodies in relation to magnetism, 255. —— the electric current, 823, 817. Cleanliness of metals and other solids, 633. Clean platina, its characters, 633, 717. ——, its power of effecting combination, 590, 605, 617, 632. ——, ——. See Plates of platina. Coal gas, brush in, 1460. ——, dark discharge in, 1556. ——, positive and negative brush in, 1476. ——, positive and negative discharge in, 1515. ——, spark in, 1422. Colladon on magnetic force of common electricity, 289. Collectors, magneto-electric, 86. Combination effected by metals, 564, 608. —— solids, 564, 618. —— poles of platina, 566. —— platina, 564, 568, 571, 590, 630. —— ——, as plates, 569. —— ——, as sponge, 609, 636. —— ——, cause of, 590, 616, 625, 656. —— ——, how, 630. —— ——, interferences with, 638, 652, 655. —— —— retarded by olefiant gas, 640. —— —— —— carbonic oxide, 645, 652. —— —— —— sulphuret of carbon, 650. —— —— —— ether, 651. —— —— —— other substances, 649, 653, 654. Comparison of voltaic batteries, 1126, 1146. Conditions, general, of voltaic decomposition, 669. ——, new, of electro-chemical decomposition, 453. Conducting power measured by a magnet, 216. —— of solid electrolytes, 419. —— of water, constant, 984. Conduction, 418, 1320. ——, its nature, 1320, 1326, 1611. ——, of two kinds, 987. ——, preceded by induction, 1329, 1332, 1338. —— and insulation, cases of the same kind, 1320, 1326, 1336, 1338, 1561. ——, its relation to the intensity of the current conducted, 419. —— common to all bodies, 444, 449. —— by a vacuum, 1613. —— by lac, 1234, 1324. —— by sulphur, 1241, 1328. —— by glass, 1239, 1324. —— by spermaceti, 1240, 1323. —— by gases, 1336. ——, slow, 1233, 1245, 1328. —— affected by temperature, 445, 1339. —— by metals diminished by heat, 432, 445. —— increased by heat, 432, 441, 445. —— of electricity and heat, relation of, 416. ——, simple, can occur in electrolytes, 967, 983. ——, —— with very feeble currents, 970. —— by electrolytes without decomposition, 968, 1017, 1032. —— and decomposition associated in electrolytes, 413, 676, 854. —— facilitated in electrolytes, 1355. —— by water bad, 1159. —— —— improved by dissolved bodies, 984, 1355. ——, electrolytic, stopped, 380, 1358, 1705. —— of currents stopped by ice, 381. —— conferred by liquefaction, 394, 410. —— taken away by solidification, 394, 1705. —— —— why, 910, 1705. ——, new law of, 380, 394, 410. ——, ——, supposed exception to, 691, 1340. ——, general results as to, 443. Conductive discharge, 1320. Conductors, electrolytic, 474. ——, magneto-electric, 86. ——, their nature does not affect the electric brush, 1454. ——, size of, affects discharge, 1372. ——, form of, affects discharge, 1374, 1425. ——, distribution of electricity on, 1368. ——, ——, affected by form, 1374. ——, ——, —— distance, 1364, 1371. ——, ——, —— air pressure, 1375. ——, ——, irregular with equal pressure, 1378. Constancy of electric current, 1618. Constitution of electrolytes as to proportions, 679, 697, 830, 1708. —— liquidity, 394, 823. Contact of metals not necessary for electrolyzation, 879. ——, its use in the voltaic battery, 893. —— not necessary for spark, 915, 956. Contiguous particles, their relation to induction, 1165, 1679. —— active in electrolysis, 1349, 1703. Convection, 1562, 1642. —— or convective discharge. See Discharge convective. Copper, iron, and sulphur circle, 943. Coruscations of lightning, 1464. Coulomb's electrometer, 1180. ——, precautions in its use, 1182, 1186, 1206. Crystals, induction through, 1689. Cube, large, electrified, 1173. Cubes of crystals, induction through, 1692, 1695. Current chemical affinity, 852, 918, 947, 996. Current, voltaic, without metallic contact, 879, 887. Current, electric, 1617. ——, defined, 282, 511. ——, nature of, 511, 667, 1617, 1627. ——, variously produced, 1618. ——, produced by chemical action, 879, 916, 1741. ——, —— animals, 351. ——, —— friction, 301, 307, 311. ——, —— heat, 349, ——, —— discharge of static electricity, 296, 307, 363. ——, —— induction by other currents, 6, 1089. ——, —— —— magnets, 30, 88, 344. ——, evolved in the moving earth, 181. ——, in the earth, 187. ——, natural standard of direction, 663. ——, none of one electricity, 1627, 1632, 1635. ——, two forces everywhere in it, 1627, 1632, 1635, 1642. ——, one, and indivisible, 1627. ——, an axis of power, 517, 1642. ——, constant in its characters, 1618, 1627. ——, inexhaustibility of, 1631. ——, its velocity in conduction, 1648. ——, —— electrolyzation, 1651. ——, regulated by a fine wire, 853, note. ——, affected by heat, 1637. ——, stopped by solidification, 381. ——, its section, 498, 504, 1634. ——, —— presents a constant force, 1634. ——, produces chemical phenomena, 1621. ——, —— heat, 1625. ——, its heating power uniform, 1630. ——, produces magnetism, 1653. ——, Porrett's effects produced by, 1646. ——, induction of, 1, 6, 232, 241, 1101, 1048. ——, ——, on itself, 1048. ——, ——. See Induction of electric current. ——, its inductive force lateral, 1108. ——, induced in different metals, 193, 213, 201, 211. ——, its transverse effects, 1653. ——, —— constant, 1655. ——, its transverse forces, 1658. ——, —— are in relation to contiguous particles, 1664. ——, —— their polarity of character, 1665. —— and magnet, their relation remembered, 38, note. Currents in air by convection, 1572, 1581. ——, metals by convection, 1603. ——, oil of turpentine by convection, 1595, 1598. Curved lines, induction in, 1215. Curves, magnetic, their relation to dynamic induction, 217, 232.

Daniell on the size of the voltaic metals, 1525. Dark discharge,1444, 1544. ——. See Discharge, dark. Dates of some facts and publications, 139, note after. Davy's theory of electro-chemical decomposition, 482, 500. —— electro-chemical views, 965. —— mercurial cones, convective phenomena, 1603. Decomposing force alike in every section of the current, 501, 505. ——, variation of, on each particle, 503. Decomposition and conduction associated in electrolytes, 413, 854. ——, primary and secondary results of, 742, 777. —— by common electricity, 309, 454. —— ——, precautions, 322. Decomposition, electro-chemical, 450, 669. ——, nomenclature of, 661. ——, new terms relating to, 662. ——, its distinguishing character, 309. ——, by common electricity, 309, 454. ——, by a single pair of plates, 862, 897, 904, 931. ——, by the electric current, 1621. ——, without metallic contact, 880, 882. ——, its cause, 891, 904, 910. ——, not due to direct attraction or repulsion of poles, 493, 497, 536, 542, 5460. ——, dependent on previous induction, 1345. ——, —— the electric current, 493, 510, 524, 854. ——, —— intensity of current, 905. ——, —— chemical affinity of particles, 519, 525, 519. ——, resistance to, 891, 910, 1007. ——, intensity requisite for, 966, 1354. ——, stopped by solidification, 380, 1358, 1705. ——, retarded by interpositions, 1007. ——, assisted by dissolved bodies, 1355. ——, division of the electrolyte, 1347, 1623, 1701. ——, transference, 519, 525, 538, 550, 1347, 1706. ——, why elements appear at the poles, 535. ——, uncombined bodies do not travel, 544, 546. ——, circular series of effects, 562, 962. ——, simultaneous, 1156, ——, definite, 329, 372, 377, 504, 704, 714, 722, 726, 732, 764, 783, 807, 821, 960. ——, —— independent of variations of electrodes, 714, 722, 807, 832. ——, necessary intensity of current, 911, 966, 1345, 1354. ——, influence of water in, 472. ——, in air, 451, 461, 469. ——, some general conditions of, 669. ——, new conditions of, 453. ——, primary results, 742. ——, secondary results, 702, 742, 748, 777. ——, of acetates, 774. ——, acetic acid, 773. ——, ammonia, 748. ——, chloride of antimony, 690, 796. ——, —— lead, 794, 815. ——, —— silver, 541, 813, 979. ——, chlorides in solution, 766. ——, —— fusion, 789, 913. ——, fused electrolytes, 789. ——, hydriodic acid and iodides, 767, 787. ——, hydrocyanic acid and cyanides, 771. ——, hydrofluoric acid and fluorides, 770. ——, iodide of lead, 802, 818. ——, —— potassium, 805. ——, muriatic acid, 758, 780. ——, nitre, 753. ——, nitric acid, 752. ——, oxide antimony, 801. ——, —— lead, 797. ——, protochloride of tin, 789, 819. ——, protiodide of tin, 804. ——, sugar, gum, &c., 776. ——, of sulphate of magnesia, 495. ——, sulphuric acid, 757. ——, sulphurous acid, 755. ——, tartaric acid, 775. ——, water, 704, 785, 807. ——, theory of, 477, 1345. ——, ——, by A. de la Rive, 489, 507, 514, 543. ——, ——, Biot, 486. ——, ——, Davy, 482, 500. ——, ——, Grotthuss, 481, 499, 515. ——, ——, Hachette, 491, 513, ——, ——, Riffault and Chompre, 485, 507, 512. ——, author's theory, 518, 524, 1345, 1623, 1703, 1766. Definite decomposing action of electricity, 329, 372, 377, 504, 704, 783, 821. ——, magnetic action of electricity, 216, 362, 367, 377. ——, electro-chemical action, 822, 869, 960. ——, ——, general principles of, 822, 862. ——, ——, in chloride of lead, 815. ——, ——, —— silver, 813. ——, ——, in hydriodic acid, 767, 787. ——, ——, iodide of lead, 802, 818. ——, ——, muriatic acid, 758, 786, ——, ——, protochloride of tin, 819. ——, ——, water, 732, 785, 807. Degree in measuring electricity, proposal for, 736. De la Rive on heat at the electrodes, 1637. ——, his theory of electro-chemical decomposition, 489, 507, 514, 543. Dielectrics, what, 1168. ——, their importance in electrical actions, 1666. ——, their relation to static induction, 1296. ——, their condition under induction, 1369, 1679. ——, their nature affects the brush, 1455. ——, their specific electric actions, 1296, 1398, 1423, 1454, 1503, 1560. Difference of positive and negative discharge, 1465, 1480, 1485. Differential inductometer, 1307. Direction of ions in the circuit, 962. ——, the electric current, 563. ——, the magneto-electric current, 114, 116. ——, the induced volta-electric current, 19, 26, 1091. Disruptive discharge, 1359, 1405. See Discharge, disruptive. Discharge, electric, as balls of fire, 1641. ——, of Leyden jar, 1300. ——, of voltaic battery by hot air, 271, 274. ——, —— points, 272. ——, velocity of, in metal, varied, 1333. ——, varieties of, 1319. ——, brush, 1425. See Brush. ——, carrying, 1562. See Discharge, convective. ——, conductive, 1320. See Conduction. ——, dark, 1444, 1544. ——, disruptive, 1359, 1405. ——, electrolytic, 1343, 1622, 1704. ——, glow, 1526. See Glow. ——, positive and negative, 1465. ——, spark, 1406. See Spark, electric. Discharge, connective, 1442, 1562, 1601, 1623, 1633, 1642. ——, in insulating media, 1562, 1572. ——, in good conductors, 1603. ——, with fluid terminations in air, 1581, 1589. ——, —— liquids, 1597. ——, from a ball, 1576, 1590. ——, influence of points in, 1573. ——, affected by mechanical causes, 1579. ——, —— flame, 1580. ——, with glow, 1576. ——, charge of a particle in air, 1564. ——, —— oil of turpentine, 1570. ——, charge of air by, 1442, 1592. ——, currents produced in air, 1572, 1581, 1591. ——, —— oil of turpentine, 1595, 1598. ——, direction of the currents, 1599, 1645. ——, Porrett's effects, 1646, ——, positive and negative, 1593, 1600, 1643. ——, related to electrolytic discharge, 1622, 1633. Discharge, dark, 1444, 1544, 1560. ——, with negative glow, 1544. ——, between positive and negative glow, 1547. ——, in air, 1548. ——, muriatic acid gas, 1554. ——, coal gas, 1556. ——, hydrogen, 1558. ——, nitrogen, 1559. Discharge, disruptive, 1405. ——, preceded by induction, 1362. ——, determined by one particle, 1370, 1409. ——, necessary intensity, 1409, 1553. ——, determining intensity constant, 1410. ——, related to particular dielectric, 1503. ——, facilitates like action, 1417, 1435, 1453, 1553. ——, its time, 1418, 1436, 1498, 1641. ——, varied by form of conductors, 1302, 1372, 1374. ——, —— change in the dielectric, 1395, 1422,1454. ——, —— rarefaction of air, 1365, 1375, 1451. ——, —— temperature, 1367, 1380. ——, —— distance of conductors, 1303, 1364, 1371. ——, —— size of conductors, 1372. ——, in liquids and solids, 1403. ——, in different gases, 1381, 1388, 1421. ——, —— not alike, 1395. ——, —— specific differences, 1399, 1422, 1687. ——, positive and negative, 1393, 1399, 1465, 1524. ——, ——, distinctions, 1467, 1475, 1482. ——, ——, differences, 1485, 1501. ——, ——, relative facility, 1496, 1520. ——, ——, dependent on the dielectric, 1503. ——, ——, in different gases, 1506, 1510, 1518, 1687. ——, ——, of voltaic current, 1524. ——, brush, 1425. ——, collateral, 1412. ——, dark, 1444, 1544, 1560. ——, glow, 1526. ——, spark, 1406. ——, theory of, 1308, 1406, 1434. Discharge, electrolytic, 1164, 1343, 1621, 1703, 1706. ——, previous induction, 1345, 1351. ——, necessary intensity, 912, 966, 1346, 1354. ——, division of the electrolyte, 1347, 1704. ——, stopped by solidifying the electrolyte, 380, 1358, 1705. ——, facilitated by added bodies, 1355. ——, in curved lines, 521, 1216, 1351. ——, proves action of contiguous particles, 1349. ——, positive and negative, 1525. ——, velocity of electric current in, 1650. ——, related to convective discharge, 1622. ——, theory of, 1344, 1622, 1704. Discharging train generally used, 292. Disruptive discharge, 1405. See Discharge, disruptive. Dissimulated electricity, 1684. Distance, its influence in induction, 1303, 1364,1371. —— over disruptive discharge, 1364, 1371. Distant chemical actions, connected and opposed, 891, 909. Distinction of magnetic and magneto-electric action, 138, 215, 243, 253. Division of a charge by inductive apparatus, 1208. Doebereiner on combination effected by platina, 609, 610. Dulong and Thenard on combination by platina and solids, 609, 611. Dust, charge of its particles, 1567.

Earth, natural magneto-electric induction in, 181, 190, 192. Elasticity of gases, 626. —— gaseous particles, 658. Electric brush, 1425. See Brush, electric. —— condition of particles of matter, 862, 1669. —— conduction, 1320. See Conduction. —— current defined, 283, 511. —— ——, nature of, 511, 1617, 1627. —— ——. See Current, electric. —— ——, induction of, 6, 232, 241, 1048, 1101. See Induction of electric current. —— ——, ——, on itself, 1048. —— discharge, 1319. See Discharge. —— force, nature of, 1667. See Forces. —— induction, 1162. See Induction. —— inductive capacity, 1252. See Specific inductive capacity. —— polarity, 1685. See Polarity, electric. —— spark, 1406. See Spark, electric. —— and magnetic forces, their relation, 118, 1411, 1653, 1658, 1709, 1731. Electrics, charge of, 1171, 1247. Electrical excitation, 1737. See Excitation. —— machine generally used, 290. —— battery generally used, 291. —— and chemical forces identical, 877, 917, 947, 960, 965, 1031. Electricities, their identity, however excited, 265, 360. ——, one or two, 516, 1667. ——, two, 1163. ——, ——, their independent existence, 1168. ——, ——, their inseparability, 1168, 1177, 1244. ——, ——, never separated in the current, 1628. Electricity, quantity of, in matter, 852, 861. ——, its distribution on conductors, 1368. ——, —— influenced by form, 1302, 1374. ——, —— —— distance, 1303, 1364, 1371. ——, —— —— air's pressure, 1375. ——, relation of a vacuum to, 1613. ——, dissimulated, 1684. ——, common and voltaic, measured, 361, 860. ——, its definite decomposing action, 329, 377, 783, 1621. ——, —— heating action, 1625. ——, —— magnetic action, 216, 366. ——, animal, its characters, 351. ——, magneto-, its characters, 343. ——, ordinary, its characters, 284. ——, thermo-, its characters, 349. ——, voltaic, its characters, 268. Electricity from magnetism, 27, 36, 57, 83, 135, 140. ——, on magnetisation of soft iron by currents, 27, 34, 57, 113. —— —— magnets, 36, 44. ——, employing permanent magnets, 39, 84, 112. ——, —— terrestrial magnetic force, 140, 150, 161. ——, —— moving conductors, 55, 83, 132, 139, 149, 161, 171. ——, —— —— essential condition, 217. —— by revolving plate, 83, 149, 240. —— —— a constant source of electricity, 89, 90, 154. —— ——, law of evolution, 114. —— ——, direction of the current evolved, 91, 99, 110, 116, 117. —— ——, course of the currents in the plate, 123, 150. —— by a revolving globe, 137, 160. —— by plates, 94, 101. —— by a wire, 49, 55, 109, 112, 137. ——, conductors and magnet may move together, 218. ——, current produced in a single wire, 49, 55, 170. ——, —— a ready source of electricity, 46, note. ——, —— momentary, 28, 30, 47. ——, —— permanent, 89, 154. ——, —— deflects galvanometer, 30, 39, 46. ——, —— makes magnets, 34. ——, ——, shock of, 56. ——, ——, spark of, 32. ——, —— traverses fluids, 23, 33. ——, ——, its direction, 30, 38, 41, 52, 53, 54, 78, 91, 99, 114, 142, 166, 220, 222. ——, effect of approximation and recession, 18, 39, 50. ——, the essential condition, 217. ——, general expression of the effects, 256. ——, from magnets alone, 220. Electricity of the voltaic pile, 875. —— its source, 875. —— —— not metallic contact, 887, 915. —— —— is in chemical action, 879, 916, 919, 1738, 1741. Electro-chemical decomposition, 450, 661. ——, nomenclature, 661. ——, general conditions of, 669. ——, new conditions of, 453, ——, influence of water in, 472. ——, primary and secondary results, 742. ——, definite, 732, 783. ——, theory of, 477. ——. See also Decomposition, electrochemical. Electro-chemical equivalents, 824, 833, 835, 855. ——, table of, 847. ——, how ascertained, 837. —— always consistent, 835. —— same as chemical equivalents, 836, 839. —— able to determine atomic number, 851. Electro-chemical excitation, 878, 919, 1738. Electrode defined, 662. Electrodes affected by heat, 1637. ——, varied in size, 714, 722. ——, —— nature, 807. ——. See Poles. Electrolysis, resistance to, 1007. Electrolyte defined, 664. —— exciting, solution of acid, 881, 925. —— —— alkali, 931, 941. —— exciting, water, 944, 945. —— —— sulphuretted solution, 943. Electrolytes, their necessary constitution, 669, 823, 829, 858, 921, 1347, 1708. —— consist of single proportionals of elements, 679, 697, 830, 1707. —— essential to voltaic pile, 921. —— ——, why, 858, 923. —— conduct and decompose simultaneously, 413. —— can conduct feeble currents without decomposition, 967. ——, as ordinary conductors, 970, 983, 1344. ——, solid, their insulating and conducting power, 419. ——, real conductive power not affected by dissolved matters, 1356. ——, needful conducting power, 1158. —— are good conductors when fluid, 394, 823. Electrolytes non-conductors when solid 381, 394. ——, why, 910, 1705. ——, the exception, 1032. Electrolytes, their particles polarize as wholes, 1700. ——, polarized light sent across, 951. ——, relation of their moving elements to the passing current, 923, 1704. ——, their resistance to decomposition, 891, 1007, 1705. ——, and metal, their states in the voltaic pile, 946. ——, salts considered as, 698. ——, acids not of this class, 681. Electrolytic action of the current, 478, 518, 1620. —— conductors, 474. —— discharge, 1343. See Discharge, electrolytic. —— induction, 1164, 1343. —— intensity, 911, 966, 983. —— —— varies for different bodies, 912, 986, 1354. —— —— of chloride of lead, 978. —— —— chloride of silver, 979. —— —— sulphate of soda, 975. —— —— water, 968, 981. —— —— its natural relation, 987. Electrolyzation, 450, 661, 1164, 1347, 1704. See Decomposition electro-chemical. —— defined, 664. —— facilitated, 394, 417, 549, 1355. —— in a single circuit, 863, 879. ——, intensity needful for, 919, 966, —— of chloride of silver, 541, 979. —— sulphate of magnesia, 495. —— and conduction associated, 413, 676. Electro-magnet, inductive effects in, 1060. Electro-magnetic induction definite, 216, 366. Electrometer, Coulomb's, described, 1180. ——, how used, 1183. Electro-tonic state, 60, 231, 242, 1114, 1661, 1729. —— considered common to all metals, 66. —— —— conductors, 76. —— is a state of tension, 71. —— is dependent on particles, 73. Elementary bodies probably ions, 849. Elements evolved by force of the current, 493, 520, 524. —— at the poles, why, 535. —— determined to either pole, 552, 681, 757. ——, transference of, 454, 538. ——, if not combined, do not travel, 544, 546. Equivalents, electro-chemical, 824, 833, 855. ——, chemical and electro-chemical, the same, 836, 839. Ether, interference of, 651. Evolution of electricity, 1162, 1737. —— of one electric force impossible, 1175. —— of elements at the poles, why, 535. Excitation, electrical, 1737. —— by chemical action, 878, 916, 1739. —— by friction, 1744. Exclusive induction, 1681.

Flame favours convectivc discharge, 1580. Flowing water, electric currents in, 190. Fluid terminations for convection, 1581. Fluids, their adhesion to metals, 1038. Fluoride of lead, hot, conducts well, 1340. Force, chemical, local, 947, 959, 1739. ——, circulating, 917, 947, 996, 1120. Force, electric, nature of, 1163, 1667. ——, inductive, of currents, its nature, 60, 1113, 1735. Forces, electric, two, 1163. ——, inseparable, 1163, 1177, 1244, 1627. —— and chemical, are the same, 877, 916. —— and magnetic, relation of, 1411, 1653, 1658, 1709. —— ——, are they essentially different? 1663, 1731. Forces, exciting, of voltaic apparatus, 887, 916. ——, exalted, 905, 994, 1138, 1148. Forces, polar, 1665. —— of the current, direct, 1620. —— ——, lateral or transverse, 1653, 1709. Form, its influence on induction, 1302, 1374. —— discharge, 1372, 1374. Fox, his terrestrial electric currents, 187. Friction electricity, its characters, 284. ——, excitement by, 1744. Fusion, conduction consequent upon, 394, 402. Fusinieri, on combination effected by platina, 613.

Galvanometer, affected by common electricity, 289, 366. ——, a correct measure of electricity, 367, note. Gases, their elasticity, 626, 657. ——, conducting power, 1336. ——, insulating power, 1381, 1507. ——, —— not alike, 1395, 1508. ——, specific inductive capacity, 1283, 1290. ——, —— alike in all, 1292. ——, specific influence on brush and spark, 1463, 1687. ——, discharge, disruptive, through, 1381. ——, brush in, 1454. ——, spark in, 1421. ——, positive and negative brushes in, 1475. ——, ——, their differences, 1476. ——, positive and negative discharge in, 1393, 1506, 1687. ——, solubility of, in cases of electrolyzation, 717, 728. ——, from water, spontaneous recombination of, 566. ——, mixtures of, affected by platina plates, 571. ——, mixed, relation of their particles, 625. General principles of definite electrolytic action, 822. —— remarks on voltaic batteries, 1031, 1136. —— results as to conduction, 443. —— —— induction, 1295. Glass, its conducting power, 1239. ——, its specific inductive capacity, 1271. ——, its attraction for air, 622. ——, —— water, 1251. Globe, revolving of Barlow, effects explained, 137, 160. ——, is magnetic, 164. Glow, 1405, 1525. ——, produced, 1527. ——, positive, 1527. ——, negative, 1530. ——, favoured by rarefaction of air, 1529. ——, is a continuous charge of air, 1526, 1537, 1543. ——, occurs in all gases, 1534. ——, accompanied by a wind, 1535. ——, its nature, 1543, ——, discharge, 1526. ——, brush and spark relation of, 1533, 1538, 1539, 1542. Grotthuss' theory of electro-chemical decomposition, 481, 499, 515. Growth of a brush, 1437. —— spark, 1553.

Hachette's view of electro-chemical decomposition, 491. Hare's voltaic trough, 1123, 1132. Harris on induction in air, 1363. Heat affects the two electrodes, 1637. —— increases the conducting power of some bodies, 432, 438, 1340. ——, its conduction related to that of electricity, 416. ——, as a result of the electric current, 853, note, 1625, 1630. —— evolved by animal electricity, 353. —— —— common electricity, 287. —— —— magneto-electricity, 344. —— —— thermo-electricity, 349. —— —— voltaic electricity, 276. Helix, inductive effects in, 1061, 1094. Hydriodic acid, its electrolyses, 767, 787. Hydrocyanic acid, its electrolyses, 771, 788. Hydrofluoric acid, not electrolysable, 770. Hydrogen, brush in, 1459. ——, positive and negative brush in, 1476. ——, —— discharge in, 1514. Hydrogen and oxygen combined by platina plates, 570, 605. —— spongy platina, 609.

Ice, its conducting power, 419. —— a non-conductor of voltaic currents, 381. Iceland crystal, induction across, 1695. Identity, of electricities, 265, 360. —— of chemical and electrical forces, 877, 917, 947, 961, 1031. Ignition of wire by electric current, 853, note, 1630. Improved voltaic battery, 1006, 1120. Increase of cells in voltaic battery, effect of, 990. Inducteous surfaces, 1483. Induction apparatus, 1187. ——, fixing the stem, 1190, 1193, 1200. ——, precautions, 1194, 1199, 1213, 1232, 1250. ——, removal of charge, 1203. ——, retention of charge, 1205, 1207. ——, a charge divided, 1208. ——, peculiar effects with, 1233. Induction, static, 1161. ——, an action of contiguous particles, 1165, 1231, 1253, 1295, 1450, 1668, 1679. ——, consists in a polarity of particles, 1298, 1670, 1679. ——, continues only in insulators, 1298, 1324, 1338. ——, intensity of, sustained, 1362. ——, influenced by the form of conductors, 1302. ——, —— distance of conductors, 1303. ——, —— relation of the bounding surfaces, 1483. ——, charge, a case of, 1171, 1177, 1300. ——, exclusive action, 1681. ——, towards space, 1614. ——, across a vacuum, 1614. —— through air, 1217, 1284. —— —— different gases, 1381, 1395. —— —— crystals, 1689, —— —— lac, 1228, 1255, 1308. —— —— metals, 1329, 1332. —— —— all bodies, 1331, 1334. ——, its relation to other electrical actions, 1165, 1178. ——, —— insulation, 1324, 13602, 1368, 1678. ——, —— conduction, 1320. ——, —— discharge, 1319, 1323, 1362. ——, —— electrolyzation, 1164, 1343. ——, —— intensity, 1178, 1362. ——, —— excitation, 1178, 1740. ——, its relation to charge, 1177, 1299. —— an essential general electric function, 1178, 1299. ——, general results as to, 1295. ——, theory of, 1165, 1231, 1295, 1667, 1669. —— in curved lines, 1166, 1215, 1679. —— ——, through air, 1218, 1449. —— ——, —— other gases, 1226. —— ——, —— lac, 1228. —— ——, —— sulphur, 1228. —— ——, —— oil of turpentine, 1227. induction, specific, 1167, 1252, 1307. ——, the problem stated, 1252. ——, —— solved, 1307. ——, of air, 1284. ——, ——, invariable, 1287, 1288. ——, of gases, 1283, 1290. ——, —— alike in all, 1292. ——, of shell-lac, 1256, 1269. ——, glass, 1271. ——, sulphur, 1275. ——, spermaceti, 1279. ——, certain fluid insulators, 1280. Induction of electric currents, 6, 34, 232, 241, 1048, 1089, 1101, 1660, 1718. ——, on aiming the principal current, 10, 238, 1101. ——, on stopping the principal current, 10, 17, 238, 1087, 1100. —— by approximation, 18, 236. —— by increasing distance, 19, 237. —— effective through conductors, 1719, 1721, 1735. —— —— insulators, 1719, 1722, 1735. —— in different metals, 193, 202, 211, 213. —— in the moving earth, 181. —— in flowing water, 190. —— in revolving plates, 85, 240. ——, the induced current, its direction, 26, 232. ——, —— duration, 19, 47, 89. ——, ——, traverses fluids, 20, 23. ——, ——, its intensity in different conductors, 183, 193, 201, 211, 213. ——, ——, not obtained by Leyden discharge, 24. ——, Ampere's results, 78, 255, 379, note. Induction of a current on itself, 1048, 1109. ——, apparatus used, 1052. ——, in a long wire, 1064, 1068, 1092, 1118. ——, —— doubled wire, 1096. ——, —— helix, 1053, 1061. —— in doubled helices, 1096. —— in an electro-magnet, 1056, 1060. ——, wire and helix compared, 1065. ——, short wire, effects with, 1067. ——, action momentary, 1070, 1091, 1100. ——, causes no permanent change in the current, 1071. ——, not due to momentum, 1077. ——, induced current separated, 1078, 1089. ——, effect at breaking contact, 1060, 1081, 1084, 1087. ——, —— making contact, 1101, 1106. ——, effects produced, shock, 1060, 1064, 1079. ——, —— spark, 1060, 1064, 1080. ——, —— chemical decomposition, 1084. ——, —— ignition of wire, 1081, 1104. ——, cause is in the conductor, 1059, 1070. ——, general principles of the action, 1093, 1107. ——, direction of the forces lateral, 1108. induction, magnetic, 255, 1658, 1710. ——, by intermediate particles, 1663, 1710, 1729, 1735. ——, through quiescent bodies, 1712, 1719, 1720, 1735. ——, —— moving bodies, 1715, 1716, 1719. —— and magneto-electric, distinguished, 138, 215, 243, 253. Induction, magneto-electric, 27, 58, 81, 140, 193, 1709. See Arago's magnetic phenomena. ——, magnelectric, 58. ——, electrolytic, 1164, 1345, 1702, 1740. ——, volta-electric, 26. Inductive capacity, specific, 1167, 1252. Inductive force of currents lateral, 26, 1108. ——, its nature, 1113, 1660, 1663, 1709. Inductive force, lines of, 1231, 1297, 1304. ——, often curved, 1219, 1224, 1230. ——, exhibited by the brush, 1449. ——, their lateral relation, 1231, 1297, 1304. ——, their relation to magnetism, 1411, 1658, 1709. Inductometer, differential, 1307, 1317. Inductric surfaces, 1483. Inexhaustible nature of the electric current, 1631. Inseparability of the two electric forces, 1163, 1177, 1244, 1628. Insulating power of different gases, 1388, 1395, 1507. Insulation, 1320, 1359, 1361. ——, its nature, 1321. —— is sustained induction, 1324. ——, degree of induction sustained, 1362. —— dependent on the dielectrics, 1368. —— —— distance in air, 1303, 1364, 1371. —— —— density of air, 1365, 1375. —— —— induction, 1368. —— —— form of conductors, 1302, 1374. ——, as affected by temperature of air, 1367, 1380. —— in different gases, 1381, 1388. —— —— differs, 1395. —— in liquids and solids, 1403. —— in metals, 1328, 1331, 1332. —— and conduction not essentially different, 1320, 1326, 1336, 1338, 1561. ——, its relation to induction, 1324, 1362, 1368, 1678. Insulators, liquid, good, 1172. ——, solid, good, 1254. ——, the best conduct, 1233, 1241, 1245, 1247, 1254. —— tested as to conduction, 1255. —— and conductors, relation of, 1328, 1334, 1338. Intensity, its influence in conduction, 419. ——, inductive, how represented, 1370. ——, relative, of magneto-electric currents, 183, 193, 211, 213. —— of disruptive discharge constant, 1410. ——, electrolytic, 912, 966, 983, 1354. —— necessary for electrolyzation, 911, 966. —— of the current of single circles, 904. —— —— increased, 906. —— of electricity in the voltaic battery, 990, 993. —— of voltaic current increased, 906, 990. Interference with combining power of platina, 638, 655. —— by olefiant gas, 640. —— carbonic oxide, 645. —— sulphuret of carbon, 650. —— ether, 651. Interpositions, their retarding effects, 1018. Iodides in solution, their electrolysis, 769. —— fusion, their electrolysis, 802, 813. Iodide of lead, electrolysed, 802, 818. —— of potassium, test of chemical action, 316. Ions, what, 665, 824, 833, 834, 849. —— not transferable alone, 542, 547, 826. ——, table of, 847. Iron, both magnetic and magneto-electric at once, 138, 254. ——, copper and sulphur circles, 943.

Jenkin, his shock by one pair of plates, 1049.

Kemp, his amalgam of zinc, 999. Knight, Dr. Gowin, his magnet, 44.

Lac, charge removed from, 1203. ——, induction through, 1255. ——, specific inductive capacity of, 1256, 1269. ——, effects of its conducting power, 1234. ——, its relation to conduction and insulation, 1324. Lateral direction of inductive forces of currents, 26, 1108. —— forces of the current, 1653, 1709. Law of conduction, new, 380, 394, 410. —— magneto-electric induction, 114. —— volta-electric induction, 26. Lead, chloride of, electrolysed, 794, 815. ——, fluoride of, conducts well when heated, 1340. ——, iodide of, electrolysed, 802, 818. ——, oxide of, electrolysed, 797. Leyden jar, condition of its charge, 1682. ——, its charge, nature of, 1300. ——, its discharge, 1300. ——, its residual charge, 1249. Light, polarized, passed across electrolytes, 951. ——, electric, 1405, 1445, 1560, note. ——, ——, spark, 1406, 1553. ——, ——, brush, 1425, 1444, 1445. ——, ——, glow, 1526. Lightning, 1420, 1404, 1641. Lines of inductive force, 1231, 1304, —— often curved, 1219, 1224, 1230. ——, as shown by the brush, 1449. ——, their lateral relation, 1231, 1297, 1304. ——, their relation to magnetism, 1411, 1658, 1709. Liquefaction, conduction consequent upon, 380, 394, 410. Liquid bodies which are non-conductors, 405. Local chemical affinity, 947, 959, 961, 1739.

Machine, electric, evolution of electricity by, 1748. ———, magneto-electric, 135, 154, 158, 1118. Magnelectric induction, 58. ——, collectors or conductors, 86. Magnesia, sulphate, decomposed against water, 494, 533. ——, transference of, 495. Magnet, a measure of conducting power, 216. —— and current, their relation remembered, 38, note. —— —— plate revolved together, 218. —— —— cylinder revolved together, 219. —— revolved alone, 220, 223. —— and moving conductors, their general relation, 256. —— made by induced current, 13, 14. ——, electricity from, 36, 220, 223. Magnetic bodies, but few, 255. ——, curves, their inductive relation, 217, 232. —— effects of voltaic electricity, 277. —— —— common electricity, 288, 367. —— —— magneto-electricity, 27, 83, 345. —— —— thermo-electricity, 349. —— —— animal electricity, 354. —— and electric forces, their relation, 118, 1411, 1653, 1658, 1709, 1731. —— forces active through intermediate particles, 1663, 1710, 1729, 1735. —— forces of the current, 1653. —— —— very constant, 1654. —— deflection by common electricity, 289, 296. —— phenomena of Arago explained, 81. —— induction. See Induction, magnetic. —— induction through quiescent bodies, 1712, 1719, 1720, 1735. —— —— moving bodies, 1715, 1719. —— and magneto-electric action distinguished, 138, 215, 243, 253. Magnetism, electricity evolved by, 27. ——, its relation to the lines of inductive force, 1411, 1658, 1709. —— bodies classed in relation to, 255. Magneto-electric currents, their intensity, 183, 193, 211, 213. ——, their direction, 114, 110. —— traverse fluids, 33. —— momentary, 30. —— permanent, 89. —— in all conductors, 193, 213. Magneto-electric induction, 27, 58. ——, terrestrial, 110, 181. ——, law of, 114. ——. See Arago's magnetic phenomena. Magneto-electric machines, 135, 154, 158. ——, inductive effects in their wires, 1118, Magneto-electricity, its general characters considered, 343, &c. —— identical with other electricities, 360. ——, its tension, 343. ——, evolution of heat, 344. ——, magnetic force, 345. ——, chemical force, 346. ——, spark, 348. ——, physiological effects, 347. ——. See Induction, magnetic. Matter, atoms of, 869, 1703. ——, new condition of, 60, 231, 242, 1114, 1661, 1729. ——, quantity of electricity in, 852, 861, 873, 1652. ——, absolute charge of, 1169. Measures of electricity, galvanometer, 367, note. ——, voltameter, 704, 736, 739. ——, metal precipitated, 740, 842. Measure of specific inductive capacity, 1307, 1600. Measurement of common and voltaic electricities, 361, 860, 1652. —— electricity, degree, 736, 738. —— —— by voltameter, 704, 736, 739. —— —— by galvanometer, 367, note. —— —— by metal precipitated, 740, 842. Mechanical forces affect chemical affinity, 656. Mercurial terminations for convection, 1581. Mercury, periodide of, an exception to the law of conduction? 691, 1341. ——, perchloride of, 692, 1341. Metallic contact not necessary for electrolyzation, 879. —— not essential to the voltaic current, 879, 887, 915. —— its use in the pile, 893, 896. Metallic poles, 557. Metal and electrolyte, their state, 946. Metals, adhesion of fluids to, 1038. ——, their power of inducing combination 564, 608. ——, —— interfered with, 638. ——, static induction in, 1329, 1332. ——, different, currents induced in, 193, 211. ——, generally secondary results of electrolysis, 746. —— transfer chemical force, 918. ——, transference of, 539, 545. —— insulate in a certain degree, 1328. ——, convective currents in, 1603. ——, but few magnetic, 255. Model of relation of magnetism and electricity, 116. Molecular inductive action, 1164, 1669. Motion essential to magneto-electric induction, 39, 217, 256. —— across magnetic curves, 217. —— of conductor and magnet, relative, 114. —— —— not necessary, 218. Moving magnet is electric, 220. Muriatic acid gas, its high insulating power, 1395. ——, brush in, 1462. ——, dark discharge in, 1554. ——, glow in, 1534. ——, positive and negative brush in, 1476. ——, spark in, 1422, 1463. ——, ——, has no dark interval, 1463, 1555. Muriatic acid decomposed by common electricity, 314. ——, its electrolysis (primary), 758, 786.

Nascent state, its relation to combination, 658, 717. Natural standard of direction for current, 663. —— relation of electrolytic intensity, 987. Nature of the electric current, 1617. —— force or forces, 1667. Negative current, none, 1627, 1632. —— discharge, 1465, 1484. —— ——, as Spark, 1467, 1482. —— ——, as brush, 1466, 1502. —— spark or brush, 1484, 1502. Negative and positive discharge, 1465, 1482, 1525 —— in different gases, 1393. New electrical condition of matter, 60, 231, 242, 1114, 1661, 1729. —— law of conduction, 380, 394, 410. Nitric acid formed by spark in air, 324. —— favours excitation of current, 906, 1138 —— —— transmission of current, 1020. —— is best for excitation of battery, 1137. ——, nature of its electrolysis, 752. Nitrogen determined to either pole, 554, 748, 752. —— a secondary result of electrolysis, 746, 748. ——, brush in, 1458. ——, dark discharge in, 1559. ——, glow in, 1534. ——, spark in, 1422, 1463. ——, positive and negative brush in, 1476. ——, —— discharge in, 1512. ——, its influence on lightning, 1464. Nomenclature, 662, 1483. Nonconduction by solid electrolytes, 381, 1358, 1705. Note on electrical excitation, 1737. Nuclei, their action, 623, 657.

Olefiant gas, interference of, 610, 652. Ordinary electricity, its tension, 285. —— evolution of heat, 287. —— magnetic force, 288, 362. —— chemical force, 309, 454. —— ——, precautions, 322. —— spark, 333. —— physiological effect, 332. —— general characters considered, 284. ——, identity with other electricities, 360. Origin of the force of the voltaic pile, 878, 910, 919. Oxidation the origin of the electric current in the voltaic pile, 919, 930. Oxide of lead electrolysed, 797. Oxygen, brush in, 1457. ——, positive and negative brush in, 1476, ——, —— discharge in, 1513. ——, solubility of, in cases of electrolyzation, 717, 728. ——, spark in, 1422. —— and hydrogen combined by platina plates, 570, 605, 630. —— —— spongy platina, 609, 636. —— —— other metals, 608.